Filament mounting for gas-detecting apparatus



April 29, 1930. w. F. HUNT ET AL I 1,756,749

FILAMENT MOUNTING FOR GAS DETECTING APPARATUS Filed Aug. 13. 1928 2 Sheets-Sheet 1 I; N IAVVENT KS: n 2 g I R Y 92,, 1%

MWA TTORAE Y5.

FILAMENT MOUNTING FOR GAS DETECTING APPARATUS Filed Aug. 13, 1928 2 Sheets-Sheet 2 INVENTORSI I I I ATTORNEVS Patented Apr. 29, 1930 7 UNITED STATES PATENT OFFICE WILEIAM E. HUNT, OF NEW DRIGHToN, AND JOHN R. MABEs, or BAYSIDE, NEW

YORK, AND WALTER IB; RowLAND, OF UPPER MoNTcLAIR, NEW JERSEY, AssIGN- oRs To OXWELID AcETYLENE COMPANY, A CORPORATION or wEsT VIRGINIA FILAIIENT MOUNTING FOR GAs- ETEGTING APPARATUS Application filed August 13, 1928. Serial No. 299,406.

i This invention relates to detectors for com- Q bustible or inflammable gases of the type in which a'heated filament is brought into contact with the atmosphere to be tested. If any combustible or inflammable gas be present the gas will be oxidized by contact with the heated filament and the temperature of said filament will be further raised. The increase in temperature depends upon the proportion of combustible or inflammable gas present and the temperature of the filament may be measured by any suitable means and in any suitable manner. However, we prefer to measure this by noting the change'in electrical resistance of said filament. While we prefer to employ-a chemically ure platinum filament and to pass a su cient electric current through it to maintain it at a temperature above 1,000 so that the oxidation proceeds without catalytic action, the present invention is not limited to the use of any particular filament material or to a temperature of above 1,000 C.

It is obvious-that if the heated filament be brought into contact with an atmosphere containing inflammable gas or gases, an explosion might be caused. For this reason we surround the filament with one or more gauze jacketsiof the type used in the well known miners flame safety lamp. .This gauze or set of gauzes serves to prevent any possibility of propagation of a flame from inside to the atmosphere outside the jackets. An object of our invention is to provide ,a mounting for the filament such that the filament-heating current cannot flow unless the protective gauze jackets are in place. Another object of our invention is to provide such a mounting that the gauze jackets cannot be removed in a shorter time than that required for the filament to cool down from the maximum temperature below that at which the inflammable constituent of the surrounding atmosphere could be ignited.

will be evident from the following description of oneembodiment of our device having.

reference to the accompanying drawingsin which: Fig. 1 is a vertical section through a device These and otherobjects of our invention constructed in accordance with one embodiment of our invention. D

Fig. 2 is a vertical section through the filament holding unit thereof.

Fig. 3 is a horizontal section of said device taken on line III-III of Fig. 1.

Fig. 4 is a side view of the device, parts being broken away, and

Fig. 5 is a perspective view of one of the gauze jackets.

In the drawings we show a mounting member 10 which is secured to a handle 11 in any suitable manner. The handle is provided with suitable means which are in fixed relation to the direction of the filament and which convey to'the operator a visual and tactile indication as to the direction of the filament.

--A block 13, preferably made of insulating material, is mounted in the member 10 and held against rotation. This block is provided with a center aperture 14 having a shoulder 15 near the bottom thereof. A shell 16 of conducting material engages the aperture below the shoulder. A helical spring 17 rests on the shoulder betweenthe shell and the upper part of the aperture. The block is also provided with one or more,side openings 18. We prefer to employ two such'o enings diametrically opposed to each other. The upper part of the opening is provided with a constricted portion or neck 19. On the. under surface of the block are mounted four conductors 21, 22, 23 and 24. Conductors 21 and 24 are each connected to one conductor of a twin conductor cable 25 which connects the detector mounting with any suitable device for measuring the change in electrical resistance of the filament and to a battery or other source of current for heating the filament. A portion of conductor 22 is in vertical alignment with but spaced from a portion of conductor 21 and a portion of conductor 23 issimilarly in vertical alignmentwith but spaced from a portion of conductor 24. The portions of the conductors which are in ver: tical alignment are preferably also in alignment with the side openings18. Each of these conductors are preferably provided with contact pieces 26 atthe points in which they are in alignment. Conductor 22 is electrically low said opening. The filament-holding unit is provided with two standards 34 and 35 for ards 34 is secured to and in electrical contact with the cup-shaped member 27. The standard 35 extends through the opening 31 and the washers 32 and 33, the standard being smaller than the opening 31 and held centrally in said opening by washers 32 and 33 whereby it is insulated from the cup-shaped member. .The standard 35 does 'not touch the cup-shaped member and the space around the standard 35 is filled with a plastic non-combustible insulating material 36. A spacing member 37 of insulatin material is provided for keeping the stan ards properly spaced. The upper portions of the standards are provided with a bearing surface 38 with which a clamping member 39 engages. The ends of a filament 41 are held between the, upper surface of the standard and the clamping member 39, the

clamping .member being held against the upper portion of the standard in'any suitable manner, as by screws 42. The ends of the standards may be held in fixed relation by spacing bars 43 which are secured to the ends of the standard in a, any suitable manner. However, we. have found that a position above and on each side of the filament is preferable. In order to support the spacers 43 the upper ends of the standards 34 and 35 are provided with upwardly and sidewardly extending arms 44 upon which the spacers {43 are mounted. The spacers are made of insulating material or insulated from the standards. The clamping member 39 fits between the arms 44.

In order to prevent propagation of flame to the surrounding atmosphere, from the gas burning at the incandescent filament, we pro vide one or more jackets of fine gauze such as are employed in'the miners flame safety lamp. While we have shown three, such jackets we do-not limit ourselves to. any par:

'ticular number as we may employ more or" le s than three. The inner jacket,-regardless o the number of jackets used, may be constructed'in accordance with the following de-- scription.

.The inner acketcomprises a jacket proper supportingthe filament. One of the stand 45 and a flanged base 46 which-is secured to it in any suitable 'manner. The center of the base is provided, with a recess to receive a collar .47 carried by the filament holding unit.

This collar can engage the recess in the base 46 in only one position or in two positions 180 apart. The collar 47 has rotatably mounted thereon a pair of screws 48 for securing the filament-holding unit to the inner jacket. The collar 47 fits the recess in the base of the jacket so closely that to remove the filament-holding unit the screws must be alternately and equally turned back a small fraction of their total travel. The total time consumed in this, together'with the other disassembling operations, is suflicient for the temperature of the filament to drop from the maximum possible operating temperature to a temperature belowfthe igniting point of the combustible components of the atmosphere. In this manner we have made it impossible for the unprotected filament while hot to come in contact with the gas-containing atmosphere. The inner jacket base also carries a pair of projections 49 which are permanently secured thereto by any suit-able means. These projections are adapted to register with and extend into the constricted portion 19 of the side openings 18 where they engage plungers 52 which are held therein by the contacts on the lower portion of the insulating block. To insure complete electrical insulation theseplungers are made of insulating material but may carry one or more wearresisting members 53, of conducting material.

Surrounding the inner jacket 45 we superimpose one or more additional jackets as 54, 54 provided with bases 55,55 adapted to rest upon the adjacent lower base. A locking ring 56 engages the outer portion of the mounting member 10 and is provided with an inwardly extending flange at the top thereof for engagement with the topmost base 55. When all the jackets are in place, and the locking ring is screwed down to the end of its travel, the inner jacket base 46 is forced downwardly, forcing the plungers downand closing the contact between conductors 21 and 22 and between conductors 23 and 24. vAt the same time the filament-holding unit is carried downwardly by the innerjacket and contact is made between the lower end ofstandard 35 and conductor 23, and between the pins 28 and the spring 17 The current may now flow from the cable through conductors 21 and 22, spring 17, pins 28, cup-shaped member 27, standard 34, filament 41, standard 35, conductors 23 and 24 and thence back to the cable. When the locking ring is unscrewed the circuit is broken in one or more of these four places and the current'is cut ofl from the filament. Moreover, due to the arrangement, of the device as set forth above, it is impossible to remove, the filament from the inner jacket before its temperature has been so reduced as to make it impossible for the surrounding gas to be ignited. The mounting member 10 is provided with a shoulder against which. the. locking ring fits when ment.

' gether, and means for holding ring that the circuit will not be closed unless the predetermined number of portective jackets are inserted around the filament.

We may provide a bonnet 57 around the gauze jackets, this bonnet being mounted upon the locking ring and phere being tested to penetrate to the fila- This bonnet serves to protect the gauze jackets from injury and also to prevent strong current of air from coming in contact with the filament. We may if we so desire provide a carrying hook 58 on the bonnet.

We have provided that the filament 41 is always in fixed relation to the handle. The filament holding unit is fixed relative to the base of the inner jacket by'the engagement between the screws 48 and the base 46. The base in turn is in fixed relation to the insulating block by engagement between projections 49 and the side apertures 18. The insulating block is fixed to the mounting member 10 which is fixed on the handle.

We claim: a

1. A head for gas'detectors comprising'a base, a protective jacket adapted to be secured to said base and a filament holding unit engaging said jacket and means holding said filament holding unit and jacket in engagement, said holding means being so situated that they can be operated only when the jacket is separated from the base.

2. A head for gas detectors comprising a block, pairs of spaced resilient conductors on said block, a filament-holding unit, a gauze jacket adapted to surround the filament, said jacket being provided with a base adapted to engagethe filament holding unit, projections extending downwardly from the base of the jacket, actuating members movably supported by the block in a position to be engaged by the projections on the base of the acket to force the spaced conductors to said jacket against said block.

3. A head for gas detectors of the type in which an electrically heated filament is exposed to the atmosphere to be tested comprising a block, a gauze jacket having its base in engagement with said block, means for supporting a filament within said jacket, conductorsincluding a switch mounted on said block and in electrical circuit with said filament, a projection on the base of said jacket and switch actuating means adapted to be engaged by said projections.

4. A device as set forth in claim 3 in which the block is provided with a vertical hole into the upper part of which the projection of the jacket base is adapted to project; and in which the switch actuating member is a rovided with. suitable apertures, for permitting the atmosplunger movably mounted in the lower part of said hole. I

5. In agas detectorhead, in combination, agauze jacket, a base for said jacket-provided with a recess, a filament holding unit, means on said unit fitting into said recess and opposed screws carried by said unit for securing said unit to the base of said jacket.

6. In a gas detector head, in combination, a gauze jacket, a base for said jacket provided with an opening, a filament-holding unit engaging said opening whereby the filament is disposed within the jacket and means for so securing said filament-holding unit to the base that the filament cannot be removed from, the jacket in less time than is required for the filament to cool from the operating temperature to a temperature that will not ignite combustible gases.

7. A head for gas detectors comprising a casing, a block within said casing, a gauze jacket having a base for engaging said block, a project-ion on said base, a plunger movably mounted within said block in a position to be engaged by said projection, a pair of normally spaced conductors opposite said plunger, and means engaging said casing for forcing the base of said jacket against said block.

8. A gas detector head comprising a block having a central aperture and' a side'aperture, a plunger mounted in the lower part of said aperture, a conductor extending below both said apertures, another conductor extending below said side aperture and spaced from said firstnamed conductor, means for supporting a filament holdin central aperture, and means xedrelatively to said filament holding unit for projecting into said side aperture for engagement with said plunger.

9. A head for gas detectors comprising a block of insulating material having a central aperture and a pair ofside apertures, a helical spring in the central aperture, a pair of spaced conductors disposed opposite each of the side apertures, one of the conductors being in circuit with said helical spring, one of the conductors of the other pair having one end disposed below said central aperture, a filament-holding unit disposed in said central aperture and provided with contacts adapted'to engage the helical. spring and the end of the conductor below the central aperture, means in said side apertures for'forcing the spaced conductors of a pair together,

a gauze jacket surrounding said filament, and,

projections carried by said jacket for engage ing the contact closing means.

10. In a head for gas detecting devices of the type in which a heatedq'filament-is exposed to the atmosphere to be't'ested, a base having a recess extending downwardly from the upper surface, means for supporting a filament above said base, a jacket surrounding said filament for preventing propagation of flame from said filament to the surround: ing outside atmosphere, said jacket being provided with a projection adapted to fit into position, and switch actuating means disposed in the bottom of said recess for closing said switch.

11. A head for gas detectors comprising, in

' combination, a base member, means for supportinga filament above said base member, a plurality of gauze jackets surrounding said filament, said jackets being. provided with basesengaging the bases of adjacent jackets, one of said bases engaging said base member, means for engaging another of said bases for holding all said bases in position on said base member, a conductor, including a switch disposed below the upper surface 'of the base member, for supplying current to said filament and a projection carried by the base of one of said jackets for operatin said switch.

12. Means for mounting a lament comprising a pair of spaced standards, means for gripping a filament on each standard, a pair of arms extending obliquely from each stand-.

ard and spacing elements connecting the arms of opposite standards.

'13. A device as set forth in claim 12 in which the filament gripping means are at the 15. A filament holding unit for a gas detecting apparatus comprising a shell, a standard ,electrically connected to said shell, a

standard within and extending through said shell, means for insulating said second standard from said shell, means intermediate the ard from said sheILmeans'intermediate the ends of the standards for holding the standards in spaced relation, arms extending obliquel from the upper ends of the standards an spacing members extending between said arms.

18. In a gas detector, a filament, conductors arranged to connect said filament with aends of the standards for holding the standards in spaced relation, means for mounting a filament between the upper ends of the standards, arms extending obliquely from the upper ends of the standards and spacing members extending between said arms.

16. A filament holding unit for a gas de- -tecting apparatus comprising a shell, a

standard electrically connected to said shell, a standard within and extending through said shell, means for insulating said second standard from said shell, means intermediate the ends of the standards for holding the standards in spaced relation and means for mounting a filament between the upper ends of the standards:

17. A filament holding unit for a gas detecting apparatus comprising a shell, a standard electrically connected to said shell, a standard within and extendin through said shell, means for insulating sai second stand- 

